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Middaugh Coaching Corner – The Science Behind a Side Stitch

Presented by Suunto

This fall, I was coaching my son’s middle school cross-country team and our last race was on a course with two big hills. The year before, Sullivan was leading the race and got a “cramp” (side stitch) about half way through the race and faded to fourth. This year, as I was explaining to him how to overcome the side stitch, I realized that most people don’t understand what it is and how to deal with it. In an XTERRA race, with the trail run as the last event, and with steep uphills that really tax your respiratory muscles and downhills that increase the jarring, it is the perfect recipe for the diaphragm spasm, or the side stitch.

A side stitch is that stabbing cramp that runners often get near the bottom of the rib cage and most often on the right side. There are a few likely theories on the mechanism of the side stitch, and it is possible that there is more than one mechanism. I will focus on the prevailing theory, which has an easy solution.

The prevailing theory is that the most likely cause of the side stitch is irritation to the parietal peritoneum most common near outer rim of the diaphragm. Your internal organs are suspended by visceral ligaments to your diaphragm. The largest and heaviest of these is your liver, which weighs about three pounds and sits on the right side. This is why the side stitch occurs most commonly on this side of the body. A stomach full of fluid and/or food can also weigh heavily on the visceral ligaments.

The diaphragm is a large, thin, dome-shaped muscle which separates the thoracic cavity from the abdomen. The dome curves upwards. When you inhale the dome contracts downward, and when you exhale the dome curves further upward. Now, imagine the tension pulling on the visceral ligaments when the dome is curved upward (exhaling) and your right leg is extended.

Your diaphragm is both an involuntary and a voluntary muscle. Most of the time it functions without our conscious control, but we can voluntarily control it at will. Simply taking voluntary control of the muscle can help alleviate a side stitch. A technique my dad taught me almost 30 years ago is to alternate which side you initiate your exhale on. This can only be done if you take voluntary control of the muscle.

Another, even more specific solution is to initiate the exhale on the opposite side as the side stitch. So if your cramp is on your right side (most common), then exhale forcefully as your left foot strikes the ground. Depending on your intensity, it probably means initiating the exhale every second time your left foot strikes the ground.

Once you have had an intense side stitch, it can make it more likely that you will experience it again. Controlling your breathing is a way to manage the cramp, but it might not completely disappear. You may need to practice these breathing techniques for several consecutive runs before the problem completely resolves. The next time it happens in a race you will at least know what it is and have something in your tool box. But please don’t slow down. The faster you run, the faster you are done. Oh, and this year Sullivan won the race – with a side stitch.

Josiah Middaugh is the 2016 XTERRA Pan America Champion and the 2015 XTERRA World Champion. He has a masters degree in kinesiology and has been a certified personal trainer for 15 years (NSCA-CSCS). His brother Yaro also has a masters degree and has been an active USAT certified coach for more than a decade. Read past training articles at and learn more about their coaching programs at

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